JP2006159570A - Molding method of sidewall member and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a molding method of a sidewall member which enables the enhancement of the adhesiveness of a different color rubber member and the efficient molding due to a series of continuous processes, in molding the sidewall member having a part different from a main body rubber in color, and a pneumatic tire constituted of the sidewall member obtained by this molding method. <P>SOLUTION: The molding method of the sidewall member comprises a process for winding a rubber strip, which is obtained by extruding a rubber having the same color as the main body rubber, around the outer periphery of a molding drum 14 along the peripheral direction of the tire to form a black rubber member 24, a process for applying surface treatment to the outer peripheral surface of the black rubber member 24 by atmospheric pressure plasma and a process for winding the rubber strip, which is obtained by extruding a rubber different from the main body rubber in color, around the outer periphery of the black rubber member 24, to which surface treatment is applied, along the peripheral direction of the tire to mold a white rubber member 26. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides a method for forming a sidewall member for constituting a pneumatic tire in which lines and characters of a color different from that of the main body rubber are formed on the sidewall portion, and a sidewall member obtained by the molding method. It is related with the pneumatic tire comprised.

  Conventionally, for the purpose of enhancing fashionability, a pneumatic tire is known in which lines and characters of a color different from that of the main rubber are formed on a sidewall portion. FIG. 5 is a cross-sectional view showing an example of such a sidewall portion. A black rubber layer 7 having the same color as that of the main body rubber and a white rubber layer 8 having a color different from that of the main body rubber are disposed on the sidewall portion 2. In addition, a thin cover rubber layer 9 having the same color as that of the main rubber is disposed outside the white rubber layer 8. After vulcanization, the cover rubber layer 9 is partially scraped off by buffing or the like, and the white rubber layer 8 is exposed, so that lines, characters, and the like can be formed on the sidewall portion 2 (Patent Document 1 below). reference).

  On the other hand, the sidewall member constituting the sidewall portion 2 is formed by an extrusion molding method or a strip build method. In the former method, as shown in FIG. 6A, after the black rubber member 24 to be the black rubber layer 7 and the white rubber member 26 to be the white rubber layer 8 are respectively extrusion molded, the outer periphery of the black rubber member 24 is formed. By attaching the white rubber member 26 and attaching the thin rubber sheet 27 to be the cover rubber layer 9 to the outer periphery thereof, the sidewall member 20 shown in FIG. 6B is formed. On the other hand, in the latter method, a rubber strip having a small width and a small thickness is used. That is, by forming a black rubber member 24 by spirally winding a black rubber strip along the tire circumferential direction, and then winding a white rubber strip around the outer periphery of the black rubber member 24, A white rubber member 26 is formed.

  However, since the sidewall member 20 has two rubber layers having different properties, that is, the black rubber layer 7 and the white rubber layer 8, the adhesion may be poor at the interface between them, and if peeling occurs at the interface, the tire There was a problem that the external appearance of this was greatly damaged. In particular, when manufacturing a pneumatic tire, after laminating the sidewall member together with the carcass ply and other rubber members, the center portion of the carcass ply is inflated and the interface peels when deformed along the tire shape. Tended to be easy.

As a countermeasure against such peeling, it is conceivable to form the sidewall member by a co-extrusion (multi-layer extrusion) molding method. In that case, it is necessary to introduce a large facility. Further, in Patent Documents 2 and 3 below, it is proposed to perform surface treatment by low-pressure plasma or corona discharge in order to improve the adhesiveness of rubber. Since it is necessary, there is a problem that the process becomes intermittent and productivity is lowered. Moreover, it is necessary to introduce a large facility such as a working chamber or a decompression device for that purpose, and it is not easy to incorporate it into a production line. Further, the treatment by corona discharge is generally performed on a flat surface, and it is not always useful when the irradiated surface has undulations like the black rubber member 24 shown in FIG.
JP-A-9-1694 JP-A-11-28770 JP 2002-220479 A

  Accordingly, an object of the present invention is to improve the adhesion of a different color rubber member when molding a side wall member having a color different from that of the main rubber, and moreover, it is efficiently molded by a series of continuous processes. An object of the present invention is to provide a method for forming a sidewall member, and a pneumatic tire constituted by the sidewall member obtained by the forming method.

  The above object can be achieved by the present invention as described below. That is, the manufacturing method of the pneumatic tire according to the present invention is a method for forming a sidewall member having a color portion different from that of the main rubber, and the first extruded rubber formed by extruding the same color rubber as the main rubber is rotated. A step of winding the outer periphery of the support body along the tire circumferential direction to form the same color rubber member, a step of subjecting the outer peripheral surface of the same color rubber member to surface treatment with atmospheric pressure plasma, and a color different from that of the main body rubber Winding a second extruded rubber formed by extruding the rubber along the tire circumferential direction around the outer periphery of the same color rubber member subjected to the surface treatment, and forming a different color rubber member.

  According to the method for producing a pneumatic tire of the present invention, first, the same color rubber member having the same color as the main rubber can be formed by winding the first extruded rubber along the tire circumferential direction. The main rubber referred to in the present invention is a rubber constituting most of the tire, and usually exhibits black. Next, the outer peripheral surface of the same color rubber member can be modified and activated by subjecting the outer peripheral surface of the same color rubber member to surface treatment with atmospheric pressure plasma. Then, by winding the second extruded rubber around the outer circumference along the tire circumferential direction, a different color rubber member having a color different from that of the main body rubber can be molded in a state in which it is well adhered to the same color rubber member. In addition, by adopting atmospheric pressure plasma that can irradiate plasma under atmospheric pressure, the transition from the process of molding the same color rubber member to the process of surface treatment is performed smoothly, and similarly, molding the different color rubber member The transition to the process is smoothly performed. Therefore, the side wall member having a color portion different from that of the main rubber can be efficiently formed by a series of continuous processes.

  In the above, a step of performing a surface treatment with atmospheric pressure plasma on the outer peripheral surface of the different color rubber member, and a thin rubber of the same color as the main body rubber on the outer periphery of the different color rubber member subjected to the surface treatment And a step of winding along the tire circumferential direction.

  According to the said structure, the outer peripheral surface of a different color rubber member can be improved and activated by performing the surface treatment by atmospheric pressure plasma with respect to the outer peripheral surface of a different color rubber member. And the thin rubber of the same color as the main body rubber is wound around the outer circumference along the tire circumferential direction, so that the thin rubber can be molded in a state of being favorably bonded to the different color rubber member. In addition, by adopting atmospheric pressure plasma that can irradiate plasma under atmospheric pressure, the transition from the step of molding the above-mentioned different color rubber member to the step of surface treatment is performed smoothly. The transition to the winding process is performed smoothly. Therefore, the side wall member having a color portion different from that of the main rubber can be efficiently formed by a series of continuous processes.

  In the above, the surface treatment with the atmospheric pressure plasma is performed by rotating and supporting the plasma emitted from the plasma irradiation means by moving the rotation support relative to the plasma irradiation means in the rotation axis direction. What irradiates helically along a tire peripheral direction with respect to the to-be-irradiated surface shape | molded on the outer peripheral side of the body is preferable.

  According to the above configuration, the surface to be irradiated formed on the outer peripheral side of the rotary support, that is, the same color rubber member or the different color rubber, by appropriately controlling the rotational speed of the rotary support and the relative movement in the rotation axis direction. Plasma can be easily and efficiently irradiated onto the outer peripheral surface of the member. Moreover, since the transition to the previous and subsequent steps becomes smoother, the molding can be performed more efficiently.

  In the above, it is preferable that the first extruded rubber and the second extruded rubber are wound in a rubber strip in a spiral shape along the tire circumferential direction.

  In the present invention, it is possible to perform extrusion molding with a desired cross-sectional shape of the same color rubber member or different color rubber member, and wrap them along the tire circumferential direction, but according to the method, there is a step in the joint portion in the tire circumferential direction. May occur. In such a case, since a step may also occur in the cover rubber layer made of a thin rubber disposed on the outer periphery of the different color rubber member, the polishing depth is increased when the cover rubber layer is polished to expose different color portions. It was necessary to flatten the surface. Therefore, the first extruded rubber and the second extruded rubber are wound in a spiral form along the tire circumferential direction in the form of a rubber strip, thereby preventing the occurrence of the above step and performing more efficient molding. Can do. Further, conventionally, when a rubber strip is wound, there is a tendency that peeling at the interface is particularly likely to occur. However, in the present invention, since the adhesiveness is improved by performing surface treatment with atmospheric pressure plasma, the rubber member Can be suitably formed.

  Further, the pneumatic tire according to the present invention includes a pair of bead portions having an annular bead, sidewall portions extending outward in the tire radial direction from the bead portions, and a tread portion provided between the sidewall portions. In the pneumatic tire provided with, the sidewall member which comprises the sidewall part was shape | molded by one of the said shaping | molding methods.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Pneumatic tire>
FIG. 1 is a meridian cross-sectional view showing an example of a pneumatic tire according to the present invention. The pneumatic tire includes a pair of bead portions 1 each including a bead 1a and a bead filler 1b, which are converging bodies of bead wires, a sidewall portion 2 extending outward from the bead portion 1 in the tire radial direction, and a sidewall. And a tread portion 3 provided between the portions 2. The carcass layer 4 is arranged so as to be bridged between the pair of bead portions 1, and the end portion is wound back via the bead 1 a. An inner liner layer 5 for maintaining air pressure is disposed on the inner peripheral side of the carcass layer 4, and a belt layer 6 that reinforces due to the effect of the warp is disposed on the outer peripheral side of the carcass layer 4. The tire structure is the same as that of a general pneumatic tire, and the present invention can be applied to any tire having the sidewall portion 2.

  As shown in FIG. 1, the pneumatic tire is composed of a plurality of rubber members, and the sidewall portion 2 is composed of a sidewall member 20. In the present embodiment, a white rubber layer 8 having a color different from that of the black main rubber is disposed on the sidewall member 20 on the right side of FIG. The white rubber layer 8 does not necessarily have to be disposed on the sidewall members 20 on both sides, and may be disposed at least on the side (the right side in the case of FIG. 1) on the vehicle outer side when mounted.

  The white rubber layer 8 is continuously arranged with a constant width along the tire circumferential direction. The cover rubber layer 9 has the same black color as the main rubber, and is thinly disposed on the outer side of the white rubber layer 8. The other part of the sidewall member 20 is a black rubber layer 7 having the same color as the main rubber. The black rubber layer 7, the white rubber layer 8, and the cover rubber layer 9 are respectively a black rubber member 24 (corresponding to the same color rubber member), a white rubber member 26 (corresponding to the different color rubber member), and a later-described black rubber member 24. It consists of a thin rubber sheet 27. After this tire is vulcanized, the cover rubber layer 9 is partially scraped off by buffing or the like, and the white rubber layer 8 is exposed, whereby white lines, letters, etc. can be formed on the sidewall portion 2. .

  The pneumatic tire according to the present invention can be formed by a conventionally known method except for the method for forming the sidewall member 20. For example, first, a rubber member to be the inner liner layer 5 is attached to the outer periphery of a cylindrical forming drum, and a carcass ply constituting the carcass layer 4 is attached to the outer periphery. Next, the sidewall member 20 obtained by the molding method of the present invention is arranged at a predetermined position with respect to the carcass ply together with other rubber members. Subsequently, an annular bead 1a is extrapolated in the vicinity of the end portion of the carcass ply, and the end portion is wound outward through the bead 1a. Then, after the center portion of the carcass ply is inflated and deformed along the tire shape, the belt layer 6 and the tread rubber are disposed on the tread surface portion. Thereafter, a line and characters of the tread pattern and the sidewall portion 2 are formed through a vulcanization process.

<Configuration of rubber member molding equipment>
FIG. 2 is a schematic view showing an example of the configuration of a rubber member molding facility for carrying out the method for molding a sidewall member according to the present invention. The rubber member molding equipment includes an extrusion device 10, a molding drum 14 (corresponding to the rotary support), an atmospheric pressure plasma processing device 15, and a control device 19.

  The extrusion apparatus 10 includes an extruder 11 and a molding die 12 connected to the distal end side of the extruder 11 in the extrusion direction. The extruder 11 has a function of kneading the unvulcanized rubber composition with a built-in screw and feeding it to the tip side. The screw is rotationally driven by the servo motor 13, and the rotational speed of the servo motor 13 is controlled by the control device 19. The unvulcanized rubber composition fed from the extruder 11 to the front end side is supplied to a molding die 12 having a predetermined cross-sectional shape and continuously extruded in the form of a rubber strip S. If necessary, a gear pump may be provided near the tip of the screw, and the unvulcanized rubber composition may be supplied to the molding die 12 via the gear pump.

  The rubber strip S is made of an unvulcanized rubber composition having a ribbon shape with a small width and a small thickness, and the width and thickness can be variously changed according to the type and size of the tire. Further, the cross-sectional shape of the rubber strip S is not particularly limited, and various and preferable shapes such as a trapezoidal shape, a crescent shape, and a rectangular shape can be adopted depending on the cross-sectional shape of the rubber member to be molded. Here, the unvulcanized rubber composition is a general rubber material such as natural rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), or isoprene rubber (IR) and its compounding material kneaded by a conventional method. These are prepared so that they can be heated and cross-linked, and various shapes such as ribbons, sheets or pellets are adopted.

  The forming drum 14 is configured to be rotatable in the R direction, and is configured to be capable of reciprocating in the rotation axis direction (a direction perpendicular to the paper surface in FIG. 2). The rotation of the forming drum 14 and the movement in the direction of the rotation axis are driven by a driving device (not shown), and are controlled by the control device 19. The rubber strip S extruded through the molding die 12 is directly supplied to the molding drum 14, and the rubber strip S is reciprocated in the rotation axis direction while rotating the molding drum 14 in the R direction. A rubber member having a desired cross-sectional shape can be formed by being spirally wound along the circumferential direction.

  The atmospheric pressure plasma processing apparatus 15 includes a generator 16, a transformer 17, and a plasma nozzle 18 (corresponding to the plasma irradiation means). The plasma nozzle 18 has a tubular casing 21, and working gas is supplied to the casing 21 from a gas supply device 22. In addition, an electrode is provided inside the casing 21, and when a high-frequency current is supplied from the generator 16 to the electrode via the transformer 17, an electric discharge is generated. The arc related to this discharge extends along the nozzle axis direction (up and down direction in FIG. 2) by the flow of the working gas, and is ejected from the opening end of the plasma nozzle 18 to become a plasma jet.

  The power supply frequency supplied to the electrode may be any of known DC and AC, and in general, a DC power supply, a low frequency (lf) power supply, a high frequency (rf) power supply, a microwave power supply, etc. are used. A power source may be used. Further, the shape and size of the generated plasma jet are not particularly limited.

  Such an atmospheric pressure plasma processing apparatus is publicly known, and for example, a plasma treat system manufactured by Agrodyn is preferred. The atmosphere gas is the atmosphere, and air is used as the working gas supplied to the plasma nozzle 18. However, the present invention is not limited to this. For example, an inert gas such as argon or helium or nitrogen gas is used. It doesn't matter.

  In the present embodiment, the plasma nozzle 18 is configured to be moved up and down by the lifting mechanism 23, and the opening end of the plasma nozzle 18 can be displaced between a position close to the forming drum 14 and a position separated from the forming drum 14. It is configured. The driving of the lifting mechanism 23 is controlled by the control device 19.

<Method of forming side wall member>
Next, a method for molding a sidewall member using the above rubber member molding equipment will be described. FIG. 3 is a flowchart illustrating an example of a procedure for molding the sidewall member. FIG. 4 is a cross-sectional view illustrating the manner in which the sidewall member is molded.

  First, an unvulcanized rubber composition for molding the black rubber member 24 is kneaded by the screw of the extruder 11 (# 1). Such an unvulcanized rubber composition uses carbon black as a compounding material and exhibits the same black color as that of the main rubber. The kneaded unvulcanized rubber composition is fed to the front end side of the extruder 11, supplied to the molding die 12, and extruded in the form of a rubber strip (corresponding to the first extruded rubber) (# 2). ). At this time, the extrusion apparatus 10 is disposed so that a predetermined interval is provided between the molding die 12 and the outer peripheral surface of the molding drum 14.

  When the tip of the extruded rubber strip sticks to the outer peripheral surface of the molding drum 14 and the winding start end of the rubber strip is fixed, the molding drum 14 is rotated in the R direction and reciprocated in the direction of the rotation axis. (# 3). The rubber strip is spirally wound around the tire circumferential direction, and the black rubber member 24 is molded as shown in FIG. 4A (# 4). The black rubber member 24 has a concave portion 25 formed in the central portion, and appropriately controls the number of revolutions of the forming drum 14 and the moving speed in the direction of the rotation axis even if it has such a undulating cross-sectional shape. Can be easily molded. When the black rubber member 24 is molded, the winding of the rubber strip is finished, and the driving of the extrusion device 10 and the molding drum 14 is stopped.

  Next, the plasma nozzle 18 is brought close to the molding drum 14, and a predetermined interval is provided between the opening end thereof and the outer peripheral surface of the black rubber member 24. The predetermined interval is set so that the plasma jet emitted from the opening end reaches the outer peripheral surface of the black rubber member 24 that is the irradiated surface, and the distance from the opening end to the irradiated surface is preferably 3. It is -40mm, More preferably, it is 5-20mm.

  When a working gas is supplied to the plasma nozzle 18 and a high-frequency current is supplied to the electrode in the casing 21, plasma is emitted from the opening end of the plasma nozzle 18 and a plasma jet is generated. At the same time, the forming drum 14 is reciprocated in the direction of the rotation axis while being driven to rotate. As a result, the plasma is irradiated spirally along the circumferential direction of the tire with respect to the irradiated surface, and surface treatment with atmospheric pressure plasma is performed (# 5). The processing speed of the surface treatment (the number of rotations of the forming drum 14) is preferably 0.1 to 100 m / min, more preferably 0.5 to 20 m / min.

  In the present embodiment, since the white rubber member 26 is formed on the outer periphery of the concave portion 25 of the black rubber member 24, at least the outer peripheral surface of the concave portion 25 is subjected to surface treatment. The plasma nozzle 18 is appropriately moved up and down according to the movement of the molding drum 14 in the direction of the rotation axis, and as shown in FIG. 4B, the plasma is appropriately applied to the outer peripheral surface of the undulating recess 25. To be controlled. When the surface treatment is completed, the plasma nozzle 18 rises and is separated from the forming drum 14.

  Subsequently, the white rubber member 26 is formed on the outer periphery of the black rubber member 24 in the same manner as the above-described # 1 to # 4. That is, the unvulcanized rubber composition is extruded in the form of a rubber strip (corresponding to the second extruded rubber), and is reciprocated in the direction of the rotation axis while rotating the molding drum 14. The white rubber member 26 is wound around the outer periphery and molded as shown in FIG. 4C (# 6, 7). However, in such an unvulcanized rubber composition, white carbon such as hydrated silicic acid or clay is used as a compounding material instead of carbon black, and it exhibits a white color different from the color of the main rubber. Therefore, it is preferable from the viewpoint of productivity that the extrusion device 10 is prepared separately for the molding of the black rubber member 24 and for the molding of the white rubber member 26 and uses them separately.

  Further, in the same manner as the above # 5, as shown in FIG. 4D, the outer peripheral surface of the white rubber member 26 is used as a surface to be irradiated, and surface treatment with atmospheric pressure plasma is performed (# 8). Then, a thin rubber sheet 27 (corresponding to the thin rubber) having a thickness of 0.2 to 3.0 mm, for example, is wound around the outer peripheral surface of the white rubber member 26 while the molding drum 14 is rotated. The wall member 20 is molded (# 9). The thin rubber sheet 27 may have a certain thickness, or may have a predetermined cross-sectional shape as shown in FIG. Such a thin rubber sheet 27 may be obtained by rolling or may be obtained by extrusion.

<Another embodiment>
(1) In this invention, it is also possible to change the cross-sectional shape of a rubber strip in the middle of winding. Further, the rubber strip supplied to the molding drum 14 may be supplied while being unwound from a workpiece that has been previously extruded and wound up.

  (2) When molding the rubber member, the molding drum 14 only needs to move relative to the extrusion device 10 in the direction of the rotation axis, and reciprocates the extrusion device 10 in the rotation axis direction of the molding drum 14. It doesn't matter. Similarly, when the surface treatment is performed, the forming drum 14 may be any one that moves relative to the plasma nozzle 18 in the direction of the rotation axis, and may reciprocate the plasma nozzle 18 in the direction of the rotation axis of the forming drum 14. I do not care.

  (3) In the above-described embodiment, the example in which the side wall member 20 is formed by winding a rubber strip having a ribbon shape with a small width and a small thickness has been described. It is also possible to wrap around a large extruded rubber. That is, a black rubber member having a cross section corresponding to the cross section of the black rubber layer may be extruded and wound along the tire circumferential direction. Alternatively, a white rubber member having a cross section corresponding to the cross section of the white rubber layer may be extruded and wound around the tire circumferential direction. In such a case, either one may be formed by a rubber strip.

  (4) The cross-sectional shape of the white rubber layer of the sidewall member molded according to the present invention is not limited to that shown in the above-described embodiment, and may be, for example, a rectangular cross-section. Further, the different color rubber member is not limited to white, and may be another color.

  (5) In the surface treatment using atmospheric pressure plasma, a plurality of plasma nozzles 18 may be used at one time. Moreover, the plasma nozzle 18 is not restricted to what is arrange | positioned at a perpendicular direction, You may make it incline suitably according to the undulation of the to-be-irradiated surface.

  In order to specifically show the configuration and effects of the present invention, a tensile test was performed based on the test method defined in JISK6251. The test piece was a dumbbell-shaped No. 3 test piece, and was collected from the vulcanized tire so that the interface between the black rubber layer and the white rubber layer was arranged at the center between the marked lines. In the test, five test pieces according to each comparative example and each example were prepared, and recorded when elongation at break (elongation when the test piece broke) and maximum stress (until the test piece was broken). The maximum tensile force to be divided by the initial cross-sectional area) was evaluated.

  A black rubber member and a white rubber member were simultaneously extruded by a co-extrusion molding method, and a test piece was collected from a tire composed of the obtained sidewall member as Comparative Example 1. In addition, a black rubber member was molded by the strip build method, a white rubber member was molded without any surface treatment on its outer periphery, and specimens collected from tires composed of the obtained sidewall members were compared. Example 2 was adopted. Then, as in the above-described embodiment, a black rubber member is molded by the strip build method, and after the surface treatment by atmospheric pressure plasma is performed on the outer periphery thereof, the white rubber member is molded, and the obtained sidewall member is configured. An example was obtained by collecting a test piece from the tire.

表１に示すように、比較例２は、比較的小さい引張力で破断しているのに対して、実施例は、比較例２と同じストリップビルド法により成形されたものでありながら、比較例１の結果と比べて遜色がなく、界面が十分に接着されていることがわかる。

As shown in Table 1, Comparative Example 2 is ruptured with a relatively small tensile force, whereas Example is formed by the same strip build method as Comparative Example 2, while Comparative Example 2 It can be seen that there is no fading compared to the result of 1 and the interface is sufficiently bonded.

The meridian cross-sectional view of the pneumatic tire according to the present invention Schematic diagram showing an example of the configuration of rubber member molding equipment Flow chart showing an example of a procedure for molding a sidewall member Sectional drawing explaining a mode that a sidewall member is shape | molded Sectional view of the side wall with a different color from the main rubber Sectional view of a side wall member having a different color part from the main rubber

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bead part 2 Side wall part 3 Tread part 7 Black rubber layer 8 White rubber layer 9 Cover rubber layer 10 Extrusion apparatus 11 Extruder 12 Molding cap 14 Molding drum 15 Atmospheric pressure plasma processing apparatus 18 Plasma nozzle 19 Control apparatus 20 Side wall Member 21 Casing 23 Elevating mechanism 24 Black rubber member 25 Recess 26 White rubber member 27 Thin rubber sheet

Claims (5)

In the method of molding a sidewall member having a different color part from the main rubber,
Winding a first extruded rubber formed by extruding rubber of the same color as the main rubber along the circumferential direction of the tire around the outer periphery of the rotating support, and molding a rubber member of the same color;
Performing a surface treatment with atmospheric pressure plasma on the outer peripheral surface of the rubber member of the same color;
Winding a second extruded rubber formed by extruding a rubber of a color different from that of the main rubber along the tire circumferential direction around the outer periphery of the same color rubber member subjected to the surface treatment, and molding a different color rubber member; A method for forming a side wall member, comprising: Performing a surface treatment with atmospheric pressure plasma on the outer peripheral surface of the different color rubber member;
A method for forming a sidewall member according to claim 1, further comprising: winding a thin rubber having the same color as that of the main body rubber around an outer periphery of the different color rubber member subjected to the surface treatment along a tire circumferential direction.   In the surface treatment with the atmospheric pressure plasma, the plasma emitted from the plasma irradiation unit is moved to the outer periphery of the rotary support by rotating the rotary support relative to the plasma irradiation unit in the direction of the rotation axis. The method for forming a sidewall member according to claim 1 or 2, wherein the surface to be irradiated is irradiated spirally along the tire circumferential direction.   The method for molding a side wall member according to any one of claims 1 to 3, wherein the first extruded rubber and the second extruded rubber are wound in a spiral shape along a tire circumferential direction in the form of a rubber strip. . In a pneumatic tire comprising a pair of bead portions having an annular bead, sidewall portions extending outward in the tire radial direction from the bead portions, and a tread portion provided between the sidewall portions,
A pneumatic tire, wherein a sidewall member constituting the sidewall portion is molded by the molding method according to any one of claims 1 to 4.

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